The new firmware improves docking compatibility, which specifically has to do with the Surface Dock, being that the Surface Laptop only uses Microsoft's proprietary Surface Connect port, rather than Thunderbolt 3, which would offer a number of docking options. Here's the full changelog:

Windows Update History Name

Device Manager Name

Surface – Firmware – 135.2139.257.0

Surface System Aggregator – Firmware

135.2139.257.0 improves docking compatibility.

According to Microsoft's value indicator chart, the update improves compatibility with no effect on security, reliability, connectivity, performance, or battery life.

Given the amount of hardware configurations that Windows 10 runs on, it's no surprise that after a feature update comes out, there are some bugs that need to be worked out with new drivers and firmware. In fact, you can expect more updates for Surface devices in the coming weeks.

To manually download the firmware and drivers package for the Surface Laptop, you can find it here.